1. Field of the Invention
The present invention relates to an image forming apparatus utilizing a solid-state scanning device for image reading.
2. Description of the Prior Art
In scanning an image with a solid-state scanning device such as a charge-coupled device, there is generally employed a method of effecting electronic principal scanning with the solid-state scanning device on the light reflected from an illuminated original and focused on said device, and also effecting auxiliary scanning in a direction perpendicular to the principal scanning direction. The image scanning is thus conducted over a determined scanning area. FIG. 1 shows an example of such scanning method, wherein there is shown an exposure lamp L, a solid-state scanning device 101, a lens 102, an original carriage 103 and an original image 104.
In such image reading apparatus, if the original image is smaller than the determined size or is incorrectly positioned, the obtained print contains unnecessary parts other than the desired original image or a part of the original image is not recorded on the recording sheet.
Also the recording sheet utilized for image recording is selected of a size meeting the size of the original image and is set in the recording unit by the operator. Consequently an error in the size selection leads to an inappropriate printing operation and the wasting of the recording sheet.
Such difficulties can only be avoided by the detection of the position of the original 4 or of the original area and non-original area and by the corresponding control of the printer, but such consideration has scarcely been made.
U.S. patent application Ser. No. 139,762 filed Apr. 14, 1980 now U.S. Pat. No. 4,325,086, issued Apr. 13, 1982, discloses an apparatus for detecting an end of the original placed on a carriage with a solid-state scanning device and accordingly controlling the record start position on the recording sheet, but such apparatus merely detects an end of the original document but is unable to detect the size thereof.